"The rapid development of multimedia and network technology has promoted the use of digital images and videos being transmitted over internet and wireless network more and more frequently. So the security of digital images and videos is needed in many applications. Recently a triple key encryption method based on logistic map was proposed. This paper analysis the security of the proposed encryption method and points out that it can be easily broken by one pair of known/chosen plain-text attack which is supported by mathematical proof and experimental result. In addition, some other security defects are also reported."